Trunked radio systems, such as the PRIVACY PLUS.TM. radio system manufactured by Motorola, Inc., allocate a plurality of communication resources (e.g., radio communication channels) amongst a group of radio users. A communication resource controller or control system, also commonly known as the trunked central controller transmits control information to radios operating in the system, usually over a control resource (also known as the control channel). A trunked radio scanning a particular control channel detects instructions from the central controller that might, for example, instruct the radio to shift to a particular communication channel whereupon the radio can transmit and receive voice and/or data information on the particular channel. Other trunked radio systems do not utilize a dedicated control channel and transmit the control information over all or select ones of the communication channels available in the system.
One particular feature known as PRIVATE CONVERSATION.TM. in the PRIVACY PLUS.TM. radio system is one in which two radio users in the system can establish a confidential, or one-to-one conversation using one of the communication channels available in the trunked radio system. During the time that the two radios are using this feature, no other radios in the trunked radio system can listen in on the conversation, thus allowing for the two radio users to have a confidential conversation.
A need exists in the art for a method and apparatus which would allow for the establishment of an exclusive and confidential communication link between more than two radios in a trunked radio system. Such a method and apparatus would allow a particular radio user to establish a conversation with a group of radio users he has selected and still be able to maintain the privacy of the conversation.